Exhaust gas discharged from an internal combustion engine of, for example, an automobile, contains toxic components such as hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). Hitherto, three-way catalysts have been used for removing such toxic components for detoxifying the exhaust gas.
In such three-way catalysts, there are some cases where a catalyst carrier made of aluminum borate is used. In one case of such a catalyst, a catalyst component is deposited on a powder compact whose particles are covered with aluminum borate whiskers and include voids therein, whereby gas diffusivity is enhanced (see Patent Document 1).
The present applicant previously proposed an exhaust gas purification catalyst carrier in which aluminum borate is modified with La2O3 in an amount, based on the mass of aluminum borate, of 0.3 to 2 mass %, preferably 0.4 to 2 mass %, more preferably 0.5 to 1.5 mass % (see Patent Document 2).